1. Field of Invention
The present invention relates to a hood exhaust method and a device thereof, and more particularly, to an air curtain-assisted exhaust method and a device thereof.
2. Related Art
Currently, in workplaces where fumes, dust, or chemical vapors present a hazard, local exhaust ventilation devices are used to prevent workers from inhaling contaminated air. Generally, an exterior exhaust hood, for example, a receiving hood, is disposed above the emission source to remove airborne contaminants. However, theoretical capture efficiency of such a receiving hood holds only in still air, the capture efficiency decreases due to crosswind in the surrounding environment, no matter how weak the crosswind is. To control the adverse effect of crosswind, a fume hood having a back panel, two side panels, and a hood sash in the front has been designed to replace a receiving hood. However, the side panels and hood sash of a fume hood limit the size of operation space for operators' upper limbs. Therefore, how to eliminate the adverse effect of crosswind, and meanwhile retain the freedom of operators' upper limbs, becomes a key topic to a receiving hood.
In order to accomplish the key topic, U.S. Pat. No. 4,788,905, published on Dec. 6, 1988, disclosed a combination cooking, eating and ventilating system. The system contains an open fire grill surrounded by an unperforated griddle, both of which are surrounded by an eating counter. A fan is positioned below the cooking grill and griddle which forces the air upward between the eating counter and the griddle in the shape of an air curtain for removing hot smoking air from the cooking area. However, due to the limited size, the fan is not applicable in a large-scale worktable. Further, generally speaking, there is not necessarily enough space to accommodate the fan device below the worktable.
Moreover, U.S. Pat. No. 5,042,456, published on Aug. 27, 1991, disclosed an air canopy ventilation system. The system comprises a surface having two substantially parallel spaced apart side panels surmounted at their respective upper edges by a canopy. A vent means having a plurality of outlets extends between the side panels and substantially the whole length of the front edge of the surface. A fan means connected to the vent means is adapted to drive a flow of air through the vent means upwardly to form a curtain of air over the front of the system, thereby entraining within the area fumes and odors. The upwardly flowing air, fumes and odors are removed by an exhaust means. Though the system can solve the problem of the lateral diffusion of the smoke and the influence of the crosswind, the air flow perpendicular to the side panel affects the efficiencies of the upward air curtain and canopy. Meanwhile, the structure of the system having the side panel and back panel limits the size of the operation space in which the operator can operate.
Further, U.S. Pat. No. 6,450,879, published on Sep. 17, 2002, disclosed an air curtain generator including a casing with a fan received therein so as to blow an air curtain from the opening of the casing, and the air curtain separates the workers and the source which generates contaminated air. However, the air curtain only isolates the smoke from laterally diffusing towards the operator, but does not isolate the smoke from diffusing towards the side without the air curtain generator. Additionally, the inventor of the present invention disclosed an air curtain generator in U.S. Pat. No. 6,752,144 published on Jun. 22, 2004, and the present invention is a continued invention along the lines of this patent.